Ensure safe_sleep tries alternative approaches (#4146)

src/Misc/layoutroot/safe_sleep.sh

@@ -1,5 +1,36 @@
 #!/bin/bash
 
+# try to use sleep if available
+if [ -x "$(command -v sleep)" ]; then
+    sleep "$1"
+    exit 0
+fi
+
+# try to use ping if available
+if [ -x "$(command -v ping)" ]; then
+    ping -c $(( $1 + 1 )) 127.0.0.1 > /dev/null
+    exit 0
+fi
+
+# try to use read -t from stdin/stdout/stderr if we are in bash
+if [ -n "$BASH_VERSION" ]; then
+    if command -v read >/dev/null 2>&1; then
+        if [ -t 0 ]; then
+            read -t "$1" -u 0 || :;
+            exit 0
+        fi
+        if [ -t 1 ]; then
+            read -t "$1" -u 1 || :;
+            exit 0
+        fi
+        if [ -t 2 ]; then
+            read -t "$1" -u 2 || :;
+            exit 0
+        fi
+    fi
+fi
+
+# fallback to a busy wait
 SECONDS=0
 while [[ $SECONDS -lt $1 ]]; do
     :